From the beginning of blood transfusions, their technique has been improved. First of all there was the preservation of blood in sterile bags of about 300 cm.sup.3 at a temperature of +4.degree. C.
For several years, the transfusion centers have separated red corpuscles from plasma, which permits transfusing only the useful part of the blood, either the concentrated red corpuscles (erythrocytes) or the plasma or serum. Apparatus to assist in the transfusion are also known, namely:
1/ pumps for accelerating the blood, to treat as rapidly as possible a hemorrhage which, when it is massive, can lead to death. These pumps of the peristaltic type in the first instance manual have been subsequently controlled by an electric motor of variable speed, electronically controlled.
2/ blood reheaters: doctors have noted that massive transfusions of cold blood lead to about 8% mortality, which is avoided with blood reheated to 37.degree. C. Moreover, clinical studies have shown that the transfusion with reheated blood decreases the transfused volume by about 30%, which decreases the risks of infection (AIDS, Hepatitis B, etc.) and is more comfortable for the patient who is no loner chilled after the procedure.
3/ on the other hand, stored blood contains micro-aggregates and impurities which it is desirable to eliminate (because they obstruct the superficial blood vessels). In addition to the conventional filter of 173 microns, so-called micro-filters of 40 microns are used.
At present, a transfusion line therefore comprises:
1/ a bag of concentrated red corpuscles, (alternatively a bag of plasma or of solution), PA1 2/ a 175 micron filter, PA1 3/ a 40 micron micro-filter, PA1 4/ a pump for accelerating the blood, PA1 5/ a blood reheater, PA1 6/ a single-use tube for the pump, PA1 7/ a single-use bag for the blood reheater (so-called blood bag) and, PA1 8/ a perfusion line connecting the assembly coupled by conical couplings of the Luer type and a trocar introduced into the vein of the patient.
The application of these different elements is long and the connection of them can sometimes lead to air leaking in, which it is absolutely necessary to eliminate because an introduction into the veins of several cubic centimeters of air is fatal.
On the other hand, all the materials occupy a large space adjacent the operating table which must be kept clear as much as possible.
All the present pumps used are of the peristaltic type, namely, conventional, with a retrograde flow during abrupt inflation of the outlet tubing at the time of disengagement of the roller, or without retrograde flow.
The pumps which have a retrograde flow require an electronic detector of the presence of air which stops the pump in case of air intake. With continuous flow pumps, having a flow rate which is always in the same direction, air bubbles can be trapped in an apparatus called an air bubble trap, which is not possible in the case of retrograde flow (or alternating flow) because the air traps then fill with air which mixes with the blood under the influence of retrograde flow during each resumed supply of the transfused liquid.
Moreover, the pump and the reheater each have adjustment and monitoring instruments as well as safety devices and alarms (luminous and sonic).